Reward Systems — the Art of Giving

Rewards!

When I play a game, I expect my experience to be a rewarding one. When a player feels rewarded, dopamine level increases in his/her brain and consequently creates a pleasurable feeling. This in turn positively reinforces the player’s behavior and keeps the player glued to the screen. This is true for everyone, but what makes an experience rewarding, exactly? Psychologists would break rewards down into these four types:

Variable Ratio Schedule

Fixed Ratio Schedule

Variable Interval Schedule

Fixed Interval Schedule

When designing a game, it is crucial to employ the right combination of reward systems that align with the gameplay. A mismatched reward system can misguide the player and easily result in a different experience regardless of the designer’s intention. For instance, if critical hits happen on a fixed timer, players will be less inclined to make more frequent attacks and wait for the timer. This creates a less action-oriented combat system.

Variable Ratio Schedule

We’re all so happy when we’re gambling.

A variable ratio reward system is powerful. It capitalizes on human behavior so well that us players are sometimes slaves to its will. In summary, a variable ratio system has an element of randomness and rewards a player after he/she performs an unpredictable number of actions. It’s the reason why casinos and gambling addictions exist. What makes variable ratio rewards so tantalizing? Turns out, dopamine levels also rise when one anticipates a reward. Being unable to predict its occurrence causes us to anticipate it on every action, keeping us on a heightened state of arousal. If we do happen to get it, the rise in dopamine level would also be higher compared to say, a fixed ratio schedule, because our brains did not expect it. The human brain is wired to be more sensitive to unexpected stimulus — this is the basis of our fight-or-flight system — it keeps us alive. The promise of a sudden, unpredictable surge of pleasurable stimulus exploits this to keep us engaged.

<3 digital cards.

In the realm of the increasingly popular “free to play with microtransactions” paradigm, variable ratio asset rewards are abused to the core. Take Hearthstone, Clash Royale and Dota 2, for example, card packs and chests give out random rewards. We know we’ll get the legendary card or epic card if we keep opening packs, but we can never predict when. So what happens next? – We keep buying and opening packs. To show how immensely effective such a model is, Hearthstone’s revenue is a sheer $24 million per month. “Oh boy a legendary!”

Oh yeah.

Variable ratio rewards are also heavily used in gameplay mechanics and have withstood the test of time. Critical hits, card drawing, and dice rolling provide players with small pleasurable moments throughout the game. With critical hits, for example, players anticipate these moments every attack. This results in a more dynamic combat experience. In Fire Emblem, I distinctly recall looking forward to the occurrence critical hits the most in combat, simply because of how it was designed — a special animation followed by four times the damage. See the animations for yourselves! It’s indescribably satisfying.

Fixed Ratio Schedule

100 coins for shrooms? I’ll take one, please.

With all the praise I’ve been giving to variable ratio rewards, surely there’s some merit for our other pals — fixed ratio rewards. Fixed ratio schedules reward players after a known, fixed number of actions. It’s basically a transaction. As explained previously, the pleasure we derive from such types of rewards is not as great compared to variable ratio rewards. However, fixed ratio systems do have an important role to play as well.

Daily quests.

Fixed ratio reward systems form the foundational experience for many games. It provides the base level of satisfaction and rewards to players, thereby promoting a consistent and predictable player behavior. A category of quests does precisely this: “Kill X boars; obtain 5 watermelons; win three games…” Take Heroes of the Storm, for instance. There are daily quests that reward us with gold for completing certain tasks a number of times, such as winning a game 3 times. If the parameters of the daily quests are unknown and the rewards are relatively small in proportion to the amount of effort invested, players are certainly not going to invest in them. Why not randomize and increase the range of rewards then variable ratio style? Well, it’s because simply inflating randomized game rewards in exchange for player commitment can cause inconsistency in terms of the basal player experience. Some players get huge rewards on a daily basis and some don’t. This unfair distribution of daily resources creates needless disadvantages for certain players.

I give up.

The allure of variable ratio reward systems can also fade rapidly, especially if players are allowed to repeatedly try for it. For an initially motivated but unlucky player, he/she can easily get tired and give up. I remember giving up Brave Frontier because it was tiring to constantly gamble for the latest units.

Variable Interval Schedules

Similar to variable ratio systems, variable interval schedule systems does a pretty good job of eliciting a slow, steady response rate from players. Variable interval schedule systems reward players repeatedly after an unpredictable period of time. This system is usually employed to motivate players to perform activities over a period of time rather than after an explicit, tangible user action. It is thus generally difficult to pinpoint these systems in games.

Finally a bite.

Treasure goblins and power shrines in Diablo 3 are examples of this. The spacing of these two elements is designed so that the player encounters them after spending an uncertain amount of time exploring uncharted areas. The player’s interest level spikes when encountering these treasures, reinforcing his behavior of exploring the map. Variable interval schedules are often used to reinforce the user’s activity within game loops in single-player focused activities. Rare encounters/respawn rates (WoW, Pokemon), air drops (for other players in H1Z1), and fishing (Stardew Valley) are instances of variable interval schedules in games.

Fixed Interval Schedules

Rewarding players after a known, predictable time period is the role of a fixed interval schedule. Unlike variable interval schedules, we know exactly when the reward will come. Since it is predictable over a fixed time period, we are usually responsive and interested when it’s close to reward time, and our interests wane sharply afterward. Furthermore, it’s not as stimulating as a surprise reward from its variable counterparts. Why would anyone use this then?

Yes. Examinations are fixed interval systems.

Many games employ the use of daily quests to incentivize us to play the game on a daily basis — a regular commitment. Fixed interval reward systems do a good job of developing player habits and commitment to a game. It is hence common to see daily quests and rewards being implemented as it encourages the development of consistent play habits and investment in a game. This is especially important in competitive multiplayer games that require a large player base. Daily rewards benefit the interested players and the developers. As players, we want that competitive edge that daily rewards give us. As developers, they want concurrent active players. As I am writing this paragraph, I was reminded that I have faithfully logged into Hearthstone daily since its launch just to not miss out on these carrots dangling in front me. Oh my god.

Another common implementation of fixed interval schedules is — leveling up. In Pokemon, the excitement when my Charmeleon is close to level 36 is immeasurable. After reaching that and evolving, the excitement dies down substantially. Across most games, leveling up is essentially a constant mini-goal that we can constantly achieve. Similar mechanics based on these mini-goal concepts include charging of ultimate abilities (Final Fantasy 10, Overwatch) and whittling down enemy HP meters. More often than not, these elements have visual elements that signify your progress bit by bit.

So which one do we use?

A combination of several layering types of reward systems seems to be the winning formula these days. Let’s use Hearthstone as an example.

We are given gold for daily quests (fixed interval) that requires us to complete certain measurable tasks such as winning a certain number of games (fixed ratio).

Opening card packs give out random rewards (variable ratio) with a possible legendary card in each pack. A pity timer is implemented to ensure that there will be at least one legendary card in 40 packs (fixed ratio).

Dust system that allows disenchanting and crafting of cards gives players a limited ability to get the cards they want after opening a large number of card packs. (fixed ratio).

Hopefully, this article provided an analysis of how your game’s rewards should be. Now, time to hand out the goodies in your game!

2 Replies to “Reward Systems — the Art of Giving”

An interesting article. The schedules you describe I have often encountered with the games I’ve played both used in combination and alone. As you have rightly pointed out, a mixed reward schedule has proven to be most effective and is employed widely across the industry and within the various games over the course of history. When reading the article, I would have liked some clarification on what you define as intervals, as ratios were amply mentioned but intervals were perhaps omitted or left to be inferred. Nevertheless, a well written informative article!

I really liked the explanation with examples of fixed with variable ratios. It brought back memories of when I was a kid and used to love buying chips packets as they used to have a gift inside it. That was like gambling in itself as I didn’t mind spending on it as I knew I would find a gift inside. Pokemon cards is another example as we never know what cards we’ll get in the booster packs but its exciting to buy and find out. I remember playing some of the games that implement fixed ratio. Pokemon Go is a game that I used to play when it first came out. It has daily quests to finish and we would get a fixed number of points, and the game also has randomness as we never know which Pokemon is nearby. But even though it implements both kinds of ratios, many people stopped playing it after some time. Maybe this combination works only for some game?